This application corresponds to German Patent Application 101 13 674.9, the entire disclosure of which is herein incorporated by reference.
1. Field of the Invention
The invention relates to an axle unit with a vehicle axle comprising a rigid axle body, developed, for example, as an axle tube having one radial arm each on both sides of the vehicle""s longitudinal mid-plane, which radial arm at a first front end is articulatable on a bearing point, stationary on the chassis, and, spaced apart therefrom, is rigidly connected with the axle body, and which forms in the region of its back end, opposing the first end, the lower support of a spring element, on whose upper side is stayed the vehicle chassis.
2. Description of Related Art
An exemplary axle unit as described above has been disclosed in EP-A-0 806 311 or EP-A-0 830 960. For example, a special axle tube can be used for the axle body, wherein the cross section or wall thickness in the region of the connection with the separate radial arms may be increased through a compression process. The radial arms are independent and essentially box-shaped, wherein the perpendicular sidewalls, bottom, and top walls are welded to one another. The rigid connection of the radial arms with the axle body is provided by at least regionally encircling circumferential welds, which require high precision in production, and which are subjected to high loads during use.
It is the object of the present invention to further develop the axle unit cited in the introduction such that production, mounting expenses, as well as the weight can be further reduced at low manufacturing costs, without diminishing the reliability and strength of the axle unit.
An axle unit in accordance with the invention includes an axle body and two radial arms, wherein the axle unit comprises two cast part halves that are connected with one another. The two cast halves may be connected together substantially horizontally, along a partition line, such that the axle body rigidly connects both radial arms with one another. In an exemplary embodiment, the two cast halves are welded together. The upper axle body half and the lower axle body half are herein also each essentially integrally connected with two upper radial arm halves and two lower radial arm halves, respectively, which complement each other.
Such shell-like cast part halves can be cost-effectively manufactured from sheet metal with suitable pressing or forging devices at low cost and in large numbers. Bracing or welding of separate radial arms with the axle body, and the work-intensive joining of the radial arms from several wall elements, such as required in the prior art arrangements, can be omitted. In an exemplary embodiment of the axle unit of the present invention, welding is only required in order to connect the two cast part halves in the region of the substantially horizontally extending partition line, in which loading is low. Furthermore, casting of the cast part halves provides a weight and load-optimizing wall thickness distribution in the axle unit. Thus it is possible to increase the material thickness in the high-load region of the connection of the radial arms with the axle body, and correspondingly to decrease it in regions that are less subject to loading. The axle unit according to the invention thereby attains high rigidity while simultaneously retains low weight.
The rigidity of the axle unit can be further increased while maintaining a relatively low weight by connecting the two cast part halves having a hollow volume. With this hollow construction, bending and torque moments, which exert an effect on the axle unit, are especially well absorbed.
If a bearing sleeve is developed or disposed at the front ends of each radial arm to connect the radial arms with the vehicle chassis, it is possible, while retaining the geometry of the axle unit, to use bearing sleeves that are individually matched to the vehicle chassis. Additionally, in this manner different materials can be used for bearing sleeves and cast part halves. In an exemplary embodiment, the bearing sleeves may be made of copper alloys. The bearing sleeves can be simply, yet securely, fastened by welding them on the radial arms, wherein the strength of the axle body is simultaneously increased.
The axle unit according to the invention can be employed in different types of vehicle chassis. Specifically, several throughbores may be provided at the back ends of the radial arms, wherein the throughbores may extend substantially perpendicularly to the plane of the partition line, in order to fasten spring elements on the radial arms. The spring elements are fastened in different throughbores, as a function of the size of the spring elements, which are preferably formed by one pneumatic spring bellows each, and the geometry of the vehicle chassis. In an exemplary embodiment, the spring elements are fastened in the through bores with a threaded stem. Due to the broad applicability of the axle unit in a variety of vehicle chassis types, the production costs, and in particular the costs for the casting tools of the cast part halves, can be kept low. Furthermore, a shock absorber attachment can take place in a manner known per se.
In order to be able to dispose a brake, such as for example a fixed caliper disk brake, in a space-saving and protected manner and in accordance with a preferred implementation of the present invention, a through-opening each is provided in the radial arms between the region connected with the axle body and the front end. Functional elements of a brake system can be accommodated in this through-opening without unnecessarily enlarging the constructional space in the region of the wheel suspension. The strength of the axle unit can be further increased by positioning an annular lining in the through-opening and welding the annular lining to the cast part halves.
An axle journal is preferably rigidly fastened in both side openings of the axle body in order to connect wheels with the axle unit. This axle journal can be pressed into the axle body, developed as an axle tube, and, if appropriate, welded to, or connected with, the axle unit in other ways. In this way, it is possible to employ differently dimensioned axle journals with a single axle unit geometry.
According to another implementation of the invention, roller bearings are provided in both side openings of the axle body. In this implementation, the wheels can be received in the bearing unit in the axle body via an extension of the wheel hub. In this development of the axle unit, the structuring of the wheels, or the brake, is also largely independent of the geometry of the axle unit, such that it can be variably employed for different vehicle types.